EXPERIMENTAL MESUREMENTS OF THE DYNAMIC PROPERTIES OF

VISCOELASTIC MATERIALS AND SYSTEMS

Imeko Technical Committee 152nd Youth Symposium on Experimental Solid MechanicsMay, 7-10 2003 Milano Marittima (Ravenna), Italy

Andrea Magalini, David Vetturi

Dipartimento di Ingegneria MeccanicaUniversità degli Studi di Brescia

2nd Youth Symposium on Experimental Solid Mechanics

2

Rubber-to-metal devices

Automotive applications: Vibrations-damping devices

• Vibrations-damping device for Mc-Pherson suspensions

• Engine mountings

• Adaptive journal boxes

2nd Youth Symposium on Experimental Solid Mechanics

3

MaterialsDynamic properties of elastomers

• Visco-elasticity

• Non - linearity

• Frequency dependence

• Temperature dependence

• Static pre-strain dependence

Hysteresis Self-heating

Str

ess

Strain

Temperature

2nd Youth Symposium on Experimental Solid Mechanics

4

Experimental analysis

Electro-dynamic shakerFixtures

Standard test-pieces

Rubber-to-metal devices

Material properties:

Sweep of sine waves at constant deformation levels

ShakerVibrating board

Test specimenSuspended mass

Device global stiffness: K*

E* G*

2nd Youth Symposium on Experimental Solid Mechanics

5

Measurement chain

Output

Accelerations System Frequency response Stiffness

Shaker

PC & Controller

Power Amplifier

ADC

Acceleration

measurement

Temperaturemeasurement

Drive signal

Power drive

Data

Test Design

DAC

2nd Youth Symposium on Experimental Solid Mechanics

6

Stiffness measurement

Suspended mass acceleration aOUT

Imposed acceleration aIN

Sine waves

System global stiffness k

System frequency response)(

)()(

IN

OUT

a

aH

0

2

4

6

8

10

12

10 100 1000

Freq. [[Hz]

Mo

du

lus

(H)

0

20

40

60

80

100

120

140

160

180

200

Ph

ase

[°]

Modulus (H)

Phase (H)

System global stiffness k()

0

500000

1000000

1500000

2000000

2500000

3000000

0 100 200 300 400 500 600

Freq. [Hz]M

od

ulu

s [N

/m]

0

2

4

6

8

10

12

Ph

ase

[°]

Modulus (k)

Phase (k)

0

2000000

4000000

6000000

8000000

10000000

12000000

14000000

16000000

0 100 200 300 400 500 600

Freq. [Hz]M

od

ulu

s [N

/m2 ]

0

2

4

6

8

10

12

Ph

ase

[°]

Modulus (E)

Phase(E)

Young’s modulus E()

2nd Youth Symposium on Experimental Solid Mechanics

7

Deformation level increase causes:

Results

140Hz - 25°C

-500

-300

-100

100

300

500

-0.2 -0.1 0 0.1 0.2

Displacement [mm]

Lo

ad

[N

]

Effects of the deformation level

• decrease of E’

• growth of E’’

Pre-strain level increase causes:

Effects of pre-strain, deformation and frequency

2

2.2

2.4

2.6

2.8

3

3.2

3.4

0 40 80 120 160 200 240 280 320

Freq. [Hz]

Pre-strain

G’ [

MP

a]

• growth of E’

2nd Youth Symposium on Experimental Solid Mechanics

8

0

2

4

6

8

10

12

14

20 25 30 35 40 45 50 55Temperature[°C]

E'[

MP

a]

E0.1mm40hz E0.1mm60hz E0.1mm100hz E0.1mm140hz E0.1mm180hz

E0.2mm40hz E0.2mm60hz E0.2mm100hz E0.2mm140hz E0.2mm180hz

2nd Youth Symposium on Experimental Solid Mechanics

9

2nd Youth Symposium on Experimental Solid Mechanics

10

Conclusions and discussions